This invention relates to a frequency detection system for detecting a frequency of an electric power system by digitally processing an electrical quantity, for example, a voltage magnitude thereof.
A conventional frequency detection system of the type referred to has comprised a rectangular waveform converter circuit for converting an AC waveform flowing through an electric power system to be detected to a rectangular waveform having a duration equal to that of a positive half cycle thereof, an "AND" circuit connected to both the rectangular waveform converter circuit and an oscillation circuit for generating a train of rectangular pulses having a predetermined pulse repetition frequency, to produce a sequence of rectangular pulse resulting from the logical sum of the rectangular waveform and the rectangular pulses, and a pulse counter for counting rectangular pulses from the "AND" circuit to produce a count in a binary form. The count from the pulse counter is compared with a frequency in a binary form set in a setting circuit to determine whether the frequency of the electric power system is higher or lower than that set in the setting circuit.
Conventional frequency detection system such as described above have been disabled to detect the absolute value of the frequency of electric power systems. Also in measuring systems including the computer to measure electrical quantities, voltages and the like can be determined and only the measurement of the frequency has required the use of a quite different instrument. However such an instrument has been unabled to be assembled in an associated computer system.
Accordingly it is an object to provide a new and improved frequency detection system for detecting a frequency of an electric power system and also determining the absolute value thereof.